1. Field of the Invention
The present invention relates to heart surgery and to cannulae used in heart surgery. The present invention relates to an improved surgical cannula, particularly a multifunctional aortic cannula. Even more particularly, the present invention relates to an improved multifunctional aortic cannula useful for open heart surgery, specifically during partial and total occlusion of the ascending aorta.
2. General Background of the Invention
Open heart procedures require flow from the heart to be interrupted to facilitate and improve operative field visibility. The present accepted practice is referred to as "cross clamping". "Cross clamping" accomplishes this task but can be damaging to the aortic structures and tissues and has potentially serious side effects.
Currently nearly all institutions use an externally applied metal occlusion clamp to occlude the aorta during open heart operations. This technique was considered to be satisfactory until information was gathered indicating that calcium from the inner wall of the aorta may become dislodged when the external clamp is applied and removed possibly causing strokes, paralysis, tissue necrosis and in some cases death.
The aortas which are heavily calcified must be treated very carefully. This danger for heart surgery patients of calcium fragments being knocked loose and causing an embolism damage to the brain and other important tissues equates into the fact that heart surgeons must treat these aortic tissues very carefully during surgery. The less manipulation and deformation these calcified aortas receive the less likely this calcium could become dislodged within the aorta. This cannula invention design will provide protection against this current problem. Surgeons have to deal with this threat to their open heart patients daily since a safer technology has not been developed, until now.
Another serious problem the patient currently must tolerate is the damage the metal occlusion clamps create by the severe unnatural deformation and stiff crushing forces that the aortas must endure.
The need therefore exists to reduce these serious problems and the associated trauma while still allowing the heart surgeon to fully or partially occlude the aorta during open heart operations performed through a sternotomy incision.
The only prior art device which attempts to solve this problem uses aortic occlusive balloon (AOB) principles, but is limited in several fundamental respects. The most significant of these problems is that the previous AOBs have no partial occlusion capabilities which this invention eliminates. Prior art devices with AOB technology are specifically designed to be introduced through a femoral catheter. Femoral insertion and placement of aortic occlusive balloon catheters increase significantly the danger of lower limb circulatory complications. Femoral catheter placement exactly into the aortic root is difficult to confirm. Correct placement must be verified with flouroscopy and/or transeophogeal echo. Femorally introduced catheter style AOBs are prone to migration within the aorta during the procedure which can cause potentially lethal side effects since continuous placement verification is necessary but is not practiced due to the technical and time constraints. The femorally introduced catheter is not designed to be introduced into the aorta under direct visualization as is this invention which eliminates the migration problems associated with previous technologies. This invention eliminates the danger and placement problems associated with femorally introduced aortic occlusion balloons which also lack the ability to partially occlude the aorta as this new technology will accomplish. Placement of this aortic occlusive balloon cannula is more accurate and safer than prior art AOBs, since the present invention is a cannula that is better secured. Optimal placement is accomplished by being physically palpated by the surgeon, and is verified under direct visualization.
Previous AOB catheters are not capable of protecting the aorta from the trauma of being overdistended especially applicable to older fragile thin walled aortas which may easily develop into an intimal tear or wall dissection and/or even more dangerous aortic rupture and death.